The invention relates in general to electrical connecting devices and in particular to a new and useful current leadthrough for refrigerators in which a plurality of conductive wires are embedded in an insulator including a base portion and insulator nub portions for each conductive wire extending upwardly from the base portion.
The invention relates particularly to a current leadthrough for refrigerators with hermetically sealed compressors. Known current leadthroughs consist of a metal base and usually three current-carrying alloyed steel pins sealed in glass.
This, however, results in difficulties when coordinating the various materials according to coefficients of expansion and in the production of a great variety of components. Moreover, joining them mechanically or chemically by means of glass sealing under pressure and in a protective gas atmosphere brings with it a considerable primary energy consumption. Overall, this adds up to relatively high costs. The sintered glass conventionally used for this purpose is of a selected porosity which can lead to electrical breakdowns if drying and sealing was imperfect. The corrosion problem must also be considered another disadvantage because the chemical nickel plating of the finished leadthrough can only lead to a qualitatively unsatisfactory compromise between surface protection and fusibility. Other difficulties result from the fact that when the leadthrough is welded into the compressor, the glass metal compound, which is under great stress, is subjected to a thermal shock which can lead to microdamages and very fine glass splinterings of the insulation with subsequent gas leaks. Furthermore, the sealing technique also requires much primary energy, a great electrode consumption and thus considerable costs overall.
Therefore, the problem underlying the present invention is seen in simplifying the production and the assembly, reducing the cost and increasing the functional safety of a current leadthrough with an insulator penetrated by electrically conducting pins. According to the invention, this is achieved in that an insulator is chosen which comprises a material having temperature stability, insensitive to chemicals and which has at least slight elasticity, in particular elastomers, thermoplastics, or the like. This affords gastight anchorage of the leadthrough in the compressor capsule and reliable electrical insulation of the current carrying pins against the compressor capsule. The glass sealing method permits only the use of steel pins, whereas the invention makes possible the arrangement of electrically better conducting brass pins.
Preferably there are disposed on a disc-shaped base one or more nubs accommodating the pins. This results in a likewise gastight connection between the pins and the nubs and, hence, of the complete leadthrough. Base and nubs are preferably molded in one piece, resulting in a particularly simple production method.
According to another characteristic of the invention, each nub has a cylindrical part and, at its free end, a conical part.
A ring-shaped bead is disposed approximately at the transition from the cylindrical to the conical part of the nub. The capsule wall contacts the nub between the disc and this bead, the latter indicating on the one hand the perfect assembly of the leadthrough while serving as resistance against the leadthrough being pushed out of the capsule on the other.
It is expedient for the base to have, at the lower cylindrical part of each nub, a ring bead oriented parallel to it. This bead serves as bearing for the capsule wall and as seal for the latter. Preferably there is provided between each pin and the leadthrough a recess of ring-shaped section, extending from the base approximately to the end of the cylindrical nub part. This facilitates the assembly of the leadthrough because it can be compressed while being inserted and it also acts as an additional seal for the capsule because the internal pressure acts upon the wall of the leadthrough. In addition, it is made possible to disassemble the leadthrough without having to destroy it. To achieve a reinforcement of the base, it has a flange which projects beyond the cylindrical part of the nub. When sealed-in pins are used, expensive contact discs must be welded on, whereas according to the invention the pins merely have upset contact surfaces.
Accordingly, an object of the invention is to provide a current leadthrough particularly for a refrigerator which comprises an insulator with a plurality of electrically conductive spaced apart pins extending through the insulator and wherein the insulator includes a base portion with an insulator nub portion for each pin extending upwardly from the base portion through which the respective pin extends and wherein the base portion is made of a temperature stable material insensitive to chemical action and which some elasticity.
A further object of the invention is to provide a current leadthrough which is simple in design, rugged in construction and economical to manufacture.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.